A digital copying machine, which is an example of a commercialized image forming apparatus, makes a copy of an original image in the following manner. Firstly, an image reading section reads an original image, secondly, an image processing section processes the read image in a specified manner, and finally, a recording section outputs information of the processed image on a sheet. In case the where a single digital copying machine is used, only the pre-installed image processing functions are available to form an image on a sheet.
On the other hand, an idea of forming a network by interconnecting a plurality of image recording apparatuses or the like has been proposed recently. For example, Japanese Laid-Open Patent Application No. 116834/1978 (Tokukaisho No. 53-116834) discloses an arrangement to interconnect a plurality of image reading apparatuses and a plurality of image recording apparatuses through a single control section. This arrangement enables each image recording apparatus to print out the original image read by any of the image reading apparatuses. Thus, the idle time of the image recording apparatuses while replacing the original documents at the image reading apparatus can be reduced.
Also, Japanese Laid-open Patent Application No. 198958/1986 (Tokukaisho No. 61-198958) discloses an image forming system including a plurality of copying machines interconnected through a single control device, and each copying machine is furnished with an image read section and an image record section. In this image forming system, image signals to be recorded are distributed to more than one copying machine furnished with a specific image copying mode the user wishes to use, and all the copying machines that received the image signals carry out the copying job in parallel.
Also, Japanese Laid-open Patent Application No. 285977/1989 (Tokukaihei 1-285977) discloses an image forming system, in which an image processing section is furnished with judging means for judging whether the image information read by an image read section can be copied or not, in other words, whether the copying of the subject image information is prohibited or not. In short, this image forming system is furnished with a function to control the copy output job of the original image based on the output from the judging means.
However, the above conventional image forming systems have the following problem.
Each image processing function of the digital copying machine depends on software programs which have been developed at an increasing pace. Thus, the image processing function is upgraded in a short period and new models with additional functions have been steadily commercialized. Therefore, the state-of-the-art digital copying machine with the desired image processing functions becomes an outdated, relatively low-level model soon after the user purchases it.
Because the user can neither upgrade the functions pre-installed in his digital copying machine nor simply add new functions, he has to purchase a new model if he wants higher level or new functions. This is an economic burden to the user and a manufacturers' problem conflicting with their efforts in trying to always meet users' demands.